Field of the Invention
The present invention relates to an arrangement and structure for an oil pan system of a vertical in-line engine when the engine is mounted in a vehicle in a horizontal or nearly horizontal attitude.
Description of the Prior Art
Japanese Patent Publication SHO 29-5711, Japanese Utility Model Publications SHO 34-19902 and SHO 46-36333 and Japanese Utility Model unexamined Publication SHO 48-29210 disclose engines which are designed originally as horizontal engines, that is, as engines intended to be mounted in a vehicle so that the pistons reciprocate in a horizontal or nearly horizontal direction. In such horizontal engines, a part of the lower side wall of the cylinder block is formed as an oil pan, or an oil pan is directly attached to the lower side wall of the cylinder block of the mounted engine.
However, when an engine which is originally designed as a vertical in-line engine is mounted in a horizontal or nearly horizontal attitude in order to conform to space available for the engine in a vehicle, an arrangement and construction has been adopted as described in the following.
FIG. 6 shows a conventional structure of a vertical in-line engine 1 with the engine mounted in a vehicle in a normal attitude, that is, uprightly. The engine 1 has a cylinder head 2, a cylinder block 3, an oil pan 4 and a piston 5. Cylinder block 3 has an opening 6 used for removing casting sand on a side wall of the cylinder block, and the opening is closed by a plug 7. An appropriate amount of oil 8 is contained in oil pan 4, and the oil level of the oil in the oil pan can be maintained at an adequate level during driving.
If the engine 1 is mounted in a vehicle in an inclined attitude keeping the construction as it is, as shown in FIG. 7, it becomes difficult to maintain the amount and the level of the oil in the oil pan 4 at adequate values. Therefore, when a vertical in-line engine is mounted in a horizontal or nearly horizontal attitude, an arrangement and structure for an oil pan system, such as a construction as shown in FIG. 8, has been adopted. In FIG. 8, an attachment member 9 is provided on the bottom portion of the cylinder block 3 , and an oil pan 10 is attached to the lower portion of the attachment member. The attachment member and the oil pan may be integrated.
In such an engine as shown in FIG. 8, however, the time for return of oil to the oil pan 10 tends to increase, because the distance (L) between the oil pan and the farthest portion to be lubricated (in this case, it is a valve mechanism) becomes greater. If the return of oil takes longer, it becomes difficult to maintain the oil level in the oil pan 10 at an adequate level, and the amount of oil to be initially contained in the oil pan must be increased.
When a vehicle mounted with an engine in the attitude shown in FIG. 8 is inclined or turned, oil in the engine may reach the state as shown in FIG. 9. That is, a large amount of oil in the oil pan 10 flows into the cylinder block 3 and/or the cylinder head 2 when the vehicle is inclined or turned, and a fairly large part of the shifted oil remains in pockets in the cylinder block and/or the cylinder head. Since this decreases the amount of oil in the oil pan 10, the delivery of oil from the oil pan to various portions of the engine may be interrupted. Also, there is a fear that increased energy loss due to interference between the displaced oil and the moving parts of the engine may deteriorate engine performance.